1. Field of Invention
The present invention relates to a pump for bicycles and, more particularly, to a pump for pumping at two pressures.
2. Related Prior Art
Cycling is a popular activity for exercising. Many people ride mountain bikes equipped with pneumatic cushions. A great proportion of such riders carry pumps on their mountain bikes for pumping tires and pneumatic pumps. A pneumatic cushion however requires less air at a higher pressure than a tire does. A nozzle designed for engagement with an inlet of a tire often fails engagement with an inlet of a pneumatic cushion for being unable to sustain such a high pressure during pumping of the pneumatic cushion. To avoid this problem, a pump may be equipped with an ordinary nozzle for engagement with an inlet of a tire and a high-pressure nozzle for engagement with an inlet of a pneumatic cushion. However, such a high-pressure nozzle is often forgotten or lost, thus rendering it impossible to pump such a pneumatic cushion. Besides, it is always troublesome to replace an ordinary nozzle with a high-pressure nozzle and vice versa. Moreover, engagement of an ordinary or high-pressure nozzle with a flexible pipe leading from such a pump becomes slack after replacement takes place for some times.
The present invention is intended to obviate or at least alleviate the problems encountered in prior art.
It is the primary objective of the present invention to provide a pump for pumping at two different pressures.
According to the present invention, a pump includes a cylinder, a piston assembly, a first nozzle, a valve, a controller, a ring and a second nozzle. The cylinder defines first and second chambers and first and second channels for communication between the chambers. The piston assembly is received in the first chamber. The first nozzle defines a channel. The valve is received in the first chamber. The controller defines an axial channel and a radial channel communicated with the axial channel, and is received in the second chamber and linked to the valve through the second channel. The controller is movable between a first position for allowing the valve to seal the second channel and a second position for driving the valve to open the second channel. The ring is mounted on the controller so as to divide the second chamber into a first portion for communication between the first channel and the channel of the first nozzle and a second portion for communication between the second channel and the radial channel of the controller. The second nozzle defines an axial channel communicated with the axial channel of the controller.
Other objects, advantages, and novel features of the invention will become apparent from the following detailed description when taken in conjunction with the attached drawings.